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Interesting article for those flying "Business Aircraft"

Piloting: Cockpit Comforts

New thinking, technologies and engineering are making ultra-long-range business jet cockpits more efficient, safer and comfortable
Jan 25, 2017Mal Gormley | Business & Commercial AviationIN
 

This article appears in the January 2017 issue of Business & Commercial Aviation with the title “Cockpit Comforts.” | Related: “Cockpit Comforts: The Hot Seat.”

 

The biggest challenge for any business aircraft manufacturer is determining how much space, comfort and amenities to dedicate to the crew and the passengers. For ultra-long-range business jets, these factors are magnified by the amount of time these aircraft spend aloft. Passengers’ needs can be met with comfortable, flexible seating and tables, good lighting and well-equipped galleys, as well as a fully functioning airborne office, fast inflight connectivity, entertainment systems and cabin controls. But the restraints of cockpit space — and until recently, technology — have limited what can be done to make the flight deck more comfortable. But that’s changing for the better.

 

New thinking and technology have combined to alter the flight deck from a functional, utilitarian space to one that offers a harmonious design aesthetic while actually enhancing information acquisition, attentiveness and control. The industry is moving toward more technologically advanced solutions such as digitally interconnected active control sidesticks and touch-screen avionics utilizing resistive input developed in real-world conditions to provide crews accuracy in turbulent flight, and is significantly recalibrating traditional cockpit seat designs for extended trips.

 

 

The evolved cockpit is the result of the advancement of human factors as a formal discipline in aviation engineering. As defined by professional ergonomist Jeff Koonce, human factors is “The study of the human’s capabilities, limitations and behaviors and the integration of that knowledge into the systems we design for them with the goals of enhancing safety, performance and the general well-being of the operators of the system.”

Aircraft designers call upon human factors guidelines to ensure functional accommodation of pilots. Medical and anthropometric research has led to today’s fully adjustable seats, for example, with vertical and horizontal positioning, as well as fully contoured pan and back cushions and a full range of articulations, including thigh angle, horizontal and vertical lumbar, headrest rotation, recline angle, articulating headrests and armrest positioning.

 

 

In addition to seating, the aircraft manufacturers are considering other components in the cockpit landscape: sidesticks, foldout workstations, the design and location of switches, functional grouping of systems controls, handholds, grips, force transducers, reading and area illumination, rest areas, lavatories and showers, and personal storage areas.

Meanwhile, the emergence of crew rest areas in ultra-long-range aircraft is a result of Advisory Circular 117-1, Flightcrew Member Rest Facilities, guidance that incorporates the latest fatigue science to set different requirements for pilot flight time, duty period and rest based on the time of day pilots begin their first flight, the number of scheduled flight segments and the number of time zones they cross.

Eliminating traditional flight control columns also has freed space for foldout workstations and more room for adjustable crew seats. Because of this, cockpits with sidesticks are roomier than ever. Ample additional storage space in the flight deck is available for each pilot in side consoles, overhead, and in dedicated crew rest and wardrobe spaces located behind the flight deck.

Take a Seat

When selecting flight deck seats for extended-range business jets, designers consider the length of time pilots will be spending in the flight deck. This confined environment subjects pilots’ spines to continued vibration and compression as well as restricted movement. Back pain is considered an occupational hazard among pilots, according to aeromedical physicians. Similar problems in the trucking industry were addressed long ago with the introduction of ergonomically designed pneumatic seating.

Studies have shown that it is possible to design ergonomically correct cockpit seating that eliminates or at least reduces pilot spine fatigue and injury. And this can be accomplished despite the recently updated FAR Part 25 and EASA certification rules requiring seats to sustain forces of a minimum of 16 Gs of acceleration; in addition, cockpit and passenger seat fabrics are required to pass stringent fire retarding standards and testing insofar as the seat foam is concerned.

 

 

Aircraft manufacturers also must consider the functionality of the seats for different activities beyond routine piloting operations. For long flights the seating must allow for relaxing or dining. And since pilots come in a wide range of sizes, the seats must accommodate people in the fifth percentile as well as those in the 95th percentile.

Ipeco, Stelia, United Technologies and Zodiac are among the leading cockpit seat makers today. Ipeco cockpit seats can be found in two dozen business and commercial aircraft types, including Alenia (ATR 42/72), Boeing (nine models), Cessna (Citation Mustang), Gulfstream (GIII, GIV, GV and G650), Hawker Beechcraft (800 and 4000), HondaJet, Pilatus (PC-12), and Tupolev (TU214). Stelia provides the cockpit seats for all of the Airbus A320 line, including the Airbus Corporate Jet. United Technology seats are in the cockpits of all Cessna Citations except the Mustang, as well as the Embraer Phenom 100 and 300 and Legacy 450 and 500, and Dassault Falcon Jets. The Embraer Lineage 600, 650 and 1000 and some Falcon Jet models have Zodiac cockpit seats.

Inceptors

Another significant development in cockpit ergonomics is the incorporation of inceptors — sidestick controls — in civilian aircraft (they’ve been used in military cockpits for years). Removing the control yokes allows for larger flight displays and moving pilot seats closer to the instrument panel, thus easing the use of touch screens. The change also provides space for an electronic flight bag (EFB) or a meal tray.

The biggest drawback of earlier, so-called passive sidesticks used in some civil aircraft was the lack of control feedback from the aircraft or the other pilot. But the transfer of “active inceptor” technology to the commercial sector from the military is helping to overcome that objection. Active sidesticks provide tactile and visual feedback in response to pilot and autopilot commands.

 

 

Gulfstream is the first civil manufacturer to adopt active sidesticks, for its new G500 and G600 business jets, and in 2010 selected BAE Systems to supply technology. Commercial inceptors are dual-duplex, using dissimilar processors so there are no common failure modes between channels. Sidestick force and position-sensing is quadruplex redundant to meet certification requirements.

The sidesticks are, obviously, digitally connected to the aircraft’s flight control systems, with dedicated links to the autopilot, pilot and copilot controls for enhanced situational awareness. The design reflects the idea of the cockpit as a cognitive system. Sidestick characteristics for breakout forces, force displacement gradients, stick-shaker and soft stops in each axis are programmable and can be tailored by the aircraft manufacturer.

Bombardier selected sidestick controls for its CSeries airliner and is incorporating fly-by-wire (FBW) and sidestick controls in its new Global 7000 and 8000 business jets. Dassault, Embraer, Bell, Sikorsky, Comac, Irkut and Sukhoi are also adoptees of the BAE Systems inceptors, and competitors are expected to soon follow suit.

Touch Screens and CCDs

Touch-screen avionics controllers reduce the number of switches on the flight deck and can act as a radio, display flight plans, perform systems checks and more, and allow pilots to directly access controls. Tablet-based interfaces logically structure input options to match only the tasks appropriate to the phase of flight. The controller panels are equipped with ergonomic frames to stabilize the pilot’s hand while using the touch screens.

Meanwhile, computer control devices (CCD) provide a means for pilots to indirectly access controls on electronic displays. Typical CCDs in the flight deck include trackballs, touch pads and joysticks.

A key benefit of CCDs is their convenience; they are typically located on or close to the pilots’ natural hand position, and are often accompanied by a hand stabilizer or armrest. This arrangement allows for convenient pilot inputs, particularly since hand and arm motion is minimized.

 

 

As with all instrumentation, CCD inputs can be erroneous, especially when the aircraft is subjected to vibration or turbulence. And these errors are more likely to go unnoticed by the other pilot because they are typically accomplished with small finger motions on the CCD. 

In addition, the FAA has encouraged avionics makers to address the problem of simultaneous “dueling cursors” during product development.

Comparisons

General comparisons of the ergonomics-driven features developed by the makers of extra-long-range business jets from Bombardier, Dassault and Gulfstream illustrate the range and similarities of approaches. The much larger Airbus Corporate Jet and Boeing BBJ offer similar amenities for their cockpit crews as well.

Bombardier

 

 

In the Global 7000 and 8000, for example, the Bombardier Vision flight deck, launched on the flagship Global 6000 in early 2012 (and also available on the company’s Learjet and Challenger aircraft), features synthetic vision system (SVS) imagery on head-up displays (HUDs), and larger display screens, providing pilots with greater situational awareness.

The Global 7000 cockpit offers a new sidestick armrest support that reduces wrist and arm fatigue and provides a better level of control for pilots. There’s also a highly portable EFB available to help pilots plan missions outside the aircraft.

 

 

Bombardier’s Global business jets offer a side-mounted jump seat outside the cockpit. This can be used by anyone facing sideways or can track and pivot into a forward- or aft-facing position, if desired. When not in use, the seat stows neatly out of the way, leaving ample room in the flight deck for ease of movement. However, citing “competitive and confidential reasons,” Bombardier declined to share additional information about its cockpit seats.

Still, a convenient grab bar above those seats on Global aircraft eases movement in and out of the cockpit. And there’s storage on the flight deck of both Global and Challenger aircraft for each pilot in the side consoles. The manufacturer also redesigned the cockpit reading lights and improved integrated map lights and side console lighting. Globals follow the dark cockpit philosophy — controls are only lit when they require the attention of the pilots.

Moreover, the Global 7000 features a 195-cu.–ft. crew rest area with two large windows, berthable seating and a forward lavatory nearby. Additional overhead compartments can be configured to provide extra storage space.

And Bombardier offers a bunk variant on Global 7000 aircraft that can accommodate an additional pair of pilots to meet the requirements of the longer missions that this aircraft is capable of achieving.

Dassault

Like Bombardier and Gulfstream, French business jet maker Dassault Falcon Jet says it has made significant changes to cockpit crew amenities as a result of extensive feedback from pilots and other crewmembers.

Its two ultra-long-range aircraft, the Falcon 7X and 8X, also feature an FBW flight control system with sidestick controllers, providing the pilots with a considerable amount of additional leg movement since they are not straddling a control column. In addition, the aircraft feature pullout tray tables, offering a generous surface area for meals, beverages and documents.

EFBs are available for both sides of the cockpit for viewing Jeppesen charts and other flight data. Falcon Sphere is a Dassault-designed EFB software suite that aggregates operational applications to support pilots on the ground and in flight. It includes Falcon flight manuals, flight documentation by aircraft serial number, access to operator-specific documentation (MELs, etc.), charts and weather apps, and more.

The cockpit seat pan cushioning has been increased by half an inch, with larger bolsters and a new material for the cushion. The designers have removed the front slit in the seat pan and used a mechanical means of fixing the cushion to prevent any local high pressure that could cause discomfort.

To further increase comfort, Dassault has added a pneumatic lumbar support and improved the foam material used on the backrest. The shape of the headrest has been improved and made adjustable. The armrests are longer and have two new positions with 7 deg. of lateral adjustment, and +/-15 degrees of vertical adjustment. The thigh rest is now controlled by a pneumatic actuator. Also, some minor changes have been made to the seat restraint system to make it more comfortable for crews.

The 7X and 8X cockpits can be configured during operation to accommodate additional recline for both front seats. The standard third flight deck seat can swivel 180 deg. and features a pop-out leg rest.

The long-legged Falcons feature a crew rest area measuring 78 in. by 30 in. When not in use, the space can be converted into a closet and storage area. A convertible crew closet is also standard on both aircraft. A crew closet and a fold-down hanger bar are standard.

Gulfstream

 

 

Meanwhile, the Gulfstream G500 and G600 feature the Symmetry Flight Deck, ushering in the company’s latest thinking in cockpit design, integration, functionality, ergonomics and aesthetics. The new design leverages active control sidesticks and touch-screen technology and will accept continual upgrades.

Meanwhile, Gulfstream-designed CCDs, standard on its long-range models, feature ergonomically angled handholds and thumb-operated force transducers that allow pilots to control the cursors on screen. And the touch-screen controller panels are equipped with ergonomic frames to stabilize the pilot’s hand while inputting commands.

The G500 and G600 cockpits also feature a new headrest with a more functional hand grab that helps pilots get in and out of the seat easier. The cockpit seat positions can be adjusted forward, aft and vertically, the backrest can recline and there is adjustable thigh support on the base cushion. Additionally, the new seats provide a full seat pan, instead of a split one, since they have replaced the control yokes with active control sidesticks.

Fixed cockpit footrests are provided on the lower area of the left-hand and right-hand instrument panels for the pilot and copilot. There is also storage space in the cockpit for small items.

 

 

All lighting in the Gulfstream G600’s crew rest area is LED and features dimming controls. Also, the controls prevent someone outside of the rest area from accidentally turning on lights or entertainment within the space and awakening someone at rest there.

The rest area meets the FAA’s requirement that the sleeping surface measure 70 in. by 30 in. and individual sleeping space volume is 35 cu. ft. A dedicated area for crew to change clothes and separate crew lavatory is available on all long-range models. The aircraft also provide computer and Wi-Fi access, charging ports for personal devices, and a monitor with headphone jack for crewmember entertainment. The rest areas on the G550 and G650/G650ER feature a window.

Sweet Spot

The science and art of keeping flight crews alert, informed, comfortable and in control has become ever more important as aircraft range — and thus mission length — has increased significantly in recent years. Manufacturers are focusing on the care and needs of the people up front more than ever. And by the end of a long mission, business aircraft crews will appreciate these thoughtful combinations of cockpit functionality, ergonomics and aesthetics that have been applied to their workspace.

 

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Don Hudson

Don Hudson

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J.O., I was a bit taken aback at the approach into Aspen - it looked really high on the display...a lot of runway visible and not the usual perspective we're accustomed to. I don't have the Aspen chart handy but if I recall from an accident there a few years ago, the approach is indeed steep. The hills off to the right are certainly imposing...Yet there it was, they sounded comfortable. I can think of a lot of fields in which this technology is going to enhance the safety of the last four miles of any approach. My buddy swears it is one of the best technologies to arrive in the cockpit in a long time.

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J.O.

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I didn't express my concern as well as I should have. I could see EVS as being a very positive addition to airline safety, especially at the marginal second and third tier airports where there just isn't enough money for infrastructure and navaids to enhance safety.

I've done the corporate aviation thing myself and know many others who've been there (or are there today). Most of us have seen both sides; the ones where the top down culture believes in safety first, and the ones where the boss will browbeat any pilot who'd dare to suggest that said boss wasn't going to get to his destination today - no matter the reason. A tool like EVS could lead some folks to push it just to make the less agreeable bosses happy.

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Seems that the new synthetic vision systems need to be used with caution:

 Limitations Of Synthetic Vision Systems

A confusing night incident in Western Australia when radalt goes awry
Mar 15, 2017Richard N. Aarons | Business & Commercial Aviation
 

In the 1960s and ’70s most sophisticated aircraft instrument panels were little different from those developed during World War II. Symbology — what there was of it — was white on a black background; attitude indicators comprised a horizon bar and aircraft symbol; directional gyros had to be caged and uncaged periodically because of precession; and pilots had to know how to fly “needle, ball and airspeed” when the vacuum gyros quit.

In spite of the relative crudeness of those old puff, blow and spin instruments, we were all taught — above all — to believe their messages (or some subset of them). You could depend on the instruments and your eyes. Your vestibular system (balance organs) and butt were not to be trusted. There was life in the instruments but unhappy endings in our internal attitude reference systems.

 

CandC_3.jpg

Today’s instruments are colorful and jam-packed with more information than most pilots can digest (See “Less is More”) These systems enable pilots to visualize their environment better then ever, but they can also suffer subtle failures that can lure the unprepared into hazardous situations.

Such was the case on June 18, 2016, at just after 0130 Australian Western Standard Time (WST), when the crew of a Pilatus PC-12 (VH-OWA) almost upset their aircraft in reaction to a faulty synthetic vision system (SVS) display.

The incident was investigated by Australia’s Transportation Safety Board (ATSB) and the story of its findings is rich in lessons for pilots flying aircraft equipped with the newest show-all display systems. What follows is largely from the ATSB investigation into the incident involving the crew of VH-OWA.

The pilot and a check pilot (who was the pilot in command) were setting out on a medical retrieval flight from Meekatharra Airport to Paraburdoo, Western Australia, under an IFR flight plan. Meekatharra Airport is in a remote area, and the airport and its surrounding terrain were dark except for a low-level wash of moonlight. The left seater was the pilot flying (PF); the check pilot was in the right seat; and a flight nurse was seated in the cabin.

 

The PF completed the pre-start, start and after-start checks while parked under a metal shed roof; however, the aircraft’s two GPS units had not acquired enough satellites to complete initialization because of the overhead cover. To correct the situation, the pilot taxied the aircraft a short distance onto the taxiway before stopping for the satellite hunt. GPS 1 located all required satellites, but GPS 2 failed to initialize and the crew received an UNABLE FMS-GPS MON caution message. The pilot followed the quick reference handbook actions in response to that message. GPS 2 initialized and the caution cleared. The pilot taxied the aircraft to Runway 9 and initiated a normal takeoff at about 0145.

Some 18 sec. after takeoff, as the Pilatus climbed through 250 ft. AGL at an airspeed of about 110 kt., the pilots observed the radio altimeter (radalt) indication wind down to zero. The radalt low-altitude awareness display on the primary flight displays (PFDs) rose to meet the altitude readout.

Simultaneously, the synthetic vision image on both pilots’ PFDs showed the runway move rapidly left and off the screen, and the ground representation on the PFD appeared to rise rapidly up to meet the zero pitch reference line (ZPRL). The pilot flying reacted automatically pulling back on the control column. The flight path indicator moved up to about 15-deg. No warnings or cautions were sounded or displayed; the stick shaker stall warning did not activate because the aircraft angle of attack (AOA) was not in the shaker range; and the crew received no oral alerts from TAWS.

The pilot flying later told investigators that the synthetic vision image created the impression that the aircraft was sinking rapidly toward the ground, and he responded by instinctively pulling back on the control column. He felt no vestibular sensation that the aircraft was descending, nor had there been any indication of a strong wind that could have caused the aircraft to drift off the runway centerline. The resulting sensory confusion caused the PF to experience a level of motion sickness.

The check pilot immediately looked outside — there was no standby instrument on the right side of the cockpit — and was able to discern a visible horizon due to the moonlight. He cautioned the PF that the aircraft had a nose-high attitude, which prompted both pilots to switch their focus to the electronic standby instrumentation system (ESIS) and closely monitor the attitude and the airspeed tape. The PF lowered the aircraft nose to regain an 8-deg. pitch attitude. Airspeed had fallen to 101 kt. during the incident and increased back to the target airspeed of 110 kt. as the pilots adjusted the pitch attitude.

The aircraft continued to climb and as it passed 850 ft., the synthetic vision display corrected itself and all indications returned to normal. After retracting the landing gear and flaps, the PF deselected the synthetic vision mode on the left PFD. The check pilot continued to monitor the synthetic vision on the right-side PFD, and the issue did not recur during the flight. The aircraft subsequently landed at Paraburdoo Airport without further incident.

The Investigation

Investigators immediately turned their attention to the radio altimeters and SVS. The first indication of trouble spotted by the pilots was the unwinding of the radalt display and the rising radalt caution crosshatches on the PFD. (See Figure 1.)

An engineering assessment determined that both radio altimeter antennas — one for transmit and one for receive — had been in service for over 9,000 hr., and had failed. The antennas did not have life limits but were required to be replaced “on condition,” which essentially meant that the antennas remained in service until they failed.

When the altitude displayed on the radalt is below 550 ft. AGL, low-altitude awareness is displayed using diagonal yellow lines (Figure 1). During this incident, the crew noticed that the low-altitude awareness symbology was displayed.

The radalt display is shown in green numbers on the PFD when the radalt data is valid and less than 2,500 ft. If the radalt data becomes invalid, the radalt digital readout is replaced with a radar altitude data (RAD) annunciator and an amber RA 1 FAIL crew alerting system (CAS) message is displayed. The crew received no annunciations during this incident to indicate that the radalt had failed.

The ATSB believes failure of the radalt antennas likely resulted in the radalt winding down to zero, and the radalt low-altitude diagonal bars to appear on the PFD altitude tape to show the aircraft was close to the ground.

Perhaps more important, the radalt information was used in conjunction with the runway and obstacle information in the TAWS database to feed the synthetic vision system. This resulted, says the ATSB, in the runway appearing to rise up toward the aircraft reference symbol on the PFD.

The synthetic vision system display is depicted in Figure 2. The PFD image provides a three-dimensional representation of surrounding terrain, obstacles and runways based on a terrain database. Normal attitude, altitude and airspeed information is overlaid on top of the terrain display. The TAWS terrain database provides geometric altitude (obtained from the GPS) in order to display synthetic vision terrain and terrain-related items such as runways and obstacles. During this incident, the synthetic vision system provided no failure annunciations.

 

The aircraft and avionics manufacturers warn pilots that the synthetic vision system is not to be used for primary input or navigation. (See Figure 3.) A similar warning was contained in the Honeywell Primus Apex Smart View supplement to the aircraft flight manual.

 

Both pilots told investigators that they were aware that the synthetic vision system should not be used for primary navigation. Interestingly, the SVS is automatically activated at start-up but can be deselected by the pilot.

Aircraft Reference Symbols

The pilot was using the flight path indicator on the SVS. This consists of the flight director command bars (magenta symbol in Figure 4) and the flight-path aircraft reference symbol (green symbol in Figure 4). The flight path indicator is a path-based mode and depicts the aircraft’s predicted flight path (not just aircraft pitch) and is affected by pitch attitude and the aircraft’s ground speed. It shows flight path angles — up for increasing and down for decreasing flight path angles, whereas the traditional pitch-based mode depicts aircraft pitch angle. The flight path angle depicted in Figure 4 is 4-deg. nose down.

 

During the departure incident, the movement of the runway to the left of the screen was probably associated with a small displacement of the aircraft to the right of the runway centerline. As the radalt senses that the aircraft is nearing the ground, smaller lateral deviations from the runway centerline generate significant movement of the synthetic vision runway image.

Engineers replaced both radalt antennas and also the radar transmitter/receiver on the incident aircraft. No subsequent similar event has occurred. The engineers also replaced the GPS 2 antenna due to slower than normal acquisition of satellite navigation after power up, and updated the GPS databases, although it was considered that these did not contribute to the incident.

The Pilots

The two pilots were highly experienced; the left-seat pilot had over 11,000 hr. total aeronautical experience and over 2,600 hr. on the aircraft type, and the check pilot had over 15,000 hr. total experience and 3,000 hr. on type.

Both pilots told investigators that they had previously experienced failure of primary flight instruments at low level and at night in different aircraft (without synthetic vision systems). They had been able to disregard the erroneous or failed instruments and reference the standby instruments to maintain control of the aircraft and situational awareness. However, the pilots told the ATSB that the prominence of the synthetic vision display was so prominent that it was difficult to ignore the erroneous information and locate valid information. Additionally, the pilot flying reported feeling a level of motion sickness, probably associated with the combined effects of the prominent synthetic vision display and conflicting vestibular sensory information.

The combination of the runway and the radalt tape moving up gave the very strong illusion that the aircraft was going to hit the ground. The PF reported that he realized something was wrong but could not initially identify it. The image of the ground rising up and the runway disappearing rapidly sideways took his focus away from anything else.

The PF commented that the check pilot’s caution “attitude” helped to redirect his attention to the standby indicator. The check pilot could not easily see the standby indicator. Both pilots commented that the situation may have been more serious if operating single-pilot or if they had already flown more sectors that night and been more fatigued.

The pilots stated that it was impossible to discern the valid attitude information on the PFD (overlaid on top of the synthetic vision) and revert to flying “power and attitude” given the prominence of the erroneous synthetic vision information. While it is possible to deselect the synthetic vision, it requires two button presses or the use of the cursor control device to do so. That is very difficult to do at low level while maintaining control of the aircraft — keeping the right hand on the thrust lever and the left hand on the control column.

Honeywell issued a Pilot Advisory Letter in response to this incident reminding pilots to look at the primary flight indications presented on the PFD at all times. The incident pilot commented that the letter should have referred pilots to the standby attitude indicator instead. The PFD display at the time of failure was simply “too confusing to start looking for two small, white attitude bars.” Similarly, to break the fixation on the erroneous information, it is important to look somewhere else at a different instrument — the standby indicator, said the pilot.

The ATSB reminds pilots that spatial disorientation can occur when visual cues provide sensory inputs that are not matched by the motion sensed by the pilot through the vestibular senses. In this case, said the Safety Board, discrepancy between the visual display showing the aircraft apparently descending toward the ground, and the lack of any consistent physical sensation, led to disorientation. The flight was conducted at night, and the pilot at the controls did not look outside for a visual reference. The check pilot did look outside and found that there was enough moonlight to provide some visual reference sufficient to show the aircraft pitch and roll attitudes relative to the horizon.

Spatial Disorientation

The ATSB research report “An Overview of Spatial Disorientation as a Factor in Aviation Accidents and Incidents” describes the spatial disorientation suffered by the crew in this incident. That is, the pilot identified that they were sensing erroneous information. The conflict between the pilots’ own perceptions and that given by the instruments alerted them to a problem, which they were then able to address. However, the crew reported feeling some level of disorientation stress, or motion sickness, which is indicative of a disagreement between the senses.

The visual system provides about 80% of orientation information, hence the overriding presence of incorrect visual information deprived the pilots of the majority of orientation information.

Other factors such as tiredness or fatigue, and high workload, can contribute to a pilot’s ability to assess and effectively deal with spatial disorientation. Both pilots commented that they wanted to share their experience because if they had been operating single pilot or near the end of a long shift, recovery from the instrumentation failure may have been much more difficult.

In addition, if the outside light conditions had been completely dark due to a lack of any moonlight in an area without terrain lighting, or the aircraft was in cloud, recognition of the spatial disorientation would have been reliant on the pilots being able to either extract the basic attitude, altitude and airspeed information from the primary display ignoring the background image, or revert to the accurate information depicted on the smaller standby indicator.

Pilots operating under Instrument Flight Rules are trained to focus their attention on the visual information presented by the aircraft instruments and to “believe” that information rather than the sensory information from the vestibular system, which can provide misleading cues.

The ATSB research report stated “instrumentation should present a clear and intuitive sense of position, which the pilot under conditions of high stress and workload can instantly achieve an idea of what the aircraft is doing.

“Failure of the aircraft instruments should hopefully never occur. However, in the event that it does, the pilot needs to receive clear and non-ambiguous indications of instrument failure. If a key instrument fails, such as the attitude indicator, the pilot needs to know that it has failed so they no longer depend on its information.”

As part of the safety actions Honeywell is investigating ways to make its synthetic vision system more robust against a similar failure. The focus of the company’s investigation is to prevent the synthetic vision display “from continuing to display the image when the data is incorrect but assessed as valid by the radar altimeter.”

Meanwhile, the ATSB reminds pilots that incorrect instrument indications that are not associated with a failure mode present pilots with a complex and challenging situation. This situation may be exacerbated during single-pilot operations, where there is a lack of external visual references (such as at night or in IMC), under high pilot workload conditions, or where a pilot is experiencing an elevated level of fatigue.

“The image of terrain on the PFD is powerful and compelling,” says the ATSB. “This incident highlights the manner in which an inaccurate synthetic vision image can rapidly lead to a degree of spatial disorientation. Pilots need to ensure that they are familiar with the limitations of the SVS and how to effectively deal with erroneous information as well as system failure modes. Organizations that operate aircraft fitted with similar technology should ensure that appropriate information and training is available to pilots, including when and how it should be used when it is not approved for primary navigation.”

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